Skeletonized internal mammary graft vs pedicled graft
Internal mammary artery (IMA) grafting is an important part of coronary artery bypass grafting. Arterial grafts give longer survival benefits compared to venous grafts. The conventional technique of IMA grafting uses pedicled grafts. Of late, skeletonized grafts are becoming more popular. The proposed advantage of skeletonized grafts is that when bilateral IMA grafts are used, there is less compromise on sternal vascularity and risk of deep sternal infections. Deep sternal infections are always a concern when using bilateral IMA grafts and can occasionally lead to sternal wound dehiscence.
Pedicled graft is harvested en-block including the associated veins and surrounding adipose tissue. Metal clips and electrocautery are used for harvesting. Vasospasm is prevented by spraying papaverine and intraluminal injection of milrinone .
Skeletonized graft is prepared using ultrasonic harmonic scalpel. The fascia around the artery is opened, vein and surrounding tissue are removed. Side branch bleeding is also controlled by the ultrasonic scalpel. Vasospasm is prevented as in case of pedicled graft. It is thought that skeletonization may preserve sternal perfusion better, especially in diabetic patients .
While pedicled grafts are typically used to graft one artery, skeletonized grafts have better mobilised length and can be used to graft multiple vessels as well as more distal coronary territories.
Proponents of total arterial revascularization always recommend the use of skeletonized internal thoracic artery (ITA – same as internal mammary artery) grafts. The advantage of skeletonization as mentioned earlier, is lesser sternal wound infection and lesser wound dehiscence while using bilateral ITA grafts, especially in diabetic patients. They also demonstrate good long term results with total arterial revascularization. But it could also be due the better surgical skill of these enthusiastic surgeons.
Concerns about theoretical downside of skeletonized grafts
Some authors have raised concerns about skeletonized grafts regarding the effect on the IMA , while the proponents of skeletonization are mostly highlighting the effects on the sternum. They argue that skeletonization deprives the IMA of its vasa vasorum, nerve supply and lymphatic drainage. There can be a imbalance between vasoconstricting and vasodilating substances reaching the vessel. The removal of associated internal thoracic vein is also thought to reduce the opportunity to drain waste products of metabolism from the IMA. Vasa vasorum of the IMA initially get supply from collateral vessels in the region. Later connections develop across the anastomotic line as well. The delay in establishing a good supply to the vessel wall can be deleterious in terms of nutrition and removal of waste products. During this interim period, nutrition and removal of waste products have to depend solely on the luminal blood, which may not be enough for the thick arterial wall. This is especially so because luminal part of the vessel wall does not have capillaries as they cant stand the high intraluminal pressure. Vasa vasorum are from the adventitial side, which is damaged by skeletonization.
- Hirose H, Amano A, Takanashi S, Takahashi A. Skeletonized bilateral internal mammary artery grafting for patients with diabetes. Interact Cardiovasc Thorac Surg. 2003 Sep;2(3):287-92.
- Cheng K, Rehman SM, Taggart DP. A Review of Differing Techniques of Mammary Artery Harvesting on Sternal Perfusion: Time for a Randomized Study? Ann Thorac Surg. 2015 Nov;100(5):1942-53.
- Tex Heart Inst J. 2003; 30(3): 170–175. Pedicled or skeletonized? A review of the internal thoracic artery graft. Tex Heart Inst J. 2003;30(3):170-5.